Quantifying Variation in Environments Within and Across Herds: Report prepared for the Co-operative Research Centre for High Integrity Australian Pork

Abstract

Animals have the ability to respond to differences in the environment, which his called environmental sensitivity. Different genotypes may not respond in the same way to diverse environments leading to genotype by environment interactions. These interactions have implications for breeding programs if animals are selected in one specific environment and progeny are expected to perform well in a wide range of environments. Breeding programs have focused on improving mean performance of pig genotypes and so far have paid little attention to incorporating environmental sensitivity in selection decisions. A number of factors such as air quality, housing, feed quality and health status define specific environmental conditions a pig may experience during the growth phase affecting its performance. Information about individual environmental factors affecting performance is usually not available on farm and other measures are required to define the quality of the environment a pig has experienced. Pigs raised together in one group or at a similar time are exposed to the same overall environmental conditions. This aspect may be used to define the quality of an environment based on the mean performance of a group of pigs. Performance records from over 265,000 pigs recorded in nine herds over a ten-year period were used for the analyses. There were genetic links between herds because a proportion of sires had progeny recorded across herds. Methodology and models were developed to quantify variation in environments within and across herds and to evaluate whether there were any breed by environment interactions or sire by environment interactions.